One of the most important current developments affecting the fields of network technologies, of call processing, and of Internet technologies, is the realization of services with real-time transmission via packet networks.
At the present moment, most speech transmission is handled via line switched networks—also known as TDM (time division multiplexing) networks. The aim for the future is to transmit a greater amount of speech via packet oriented networks which are currently used mainly for data transmission. Hereby, the so called IP (Internet protocol) networks are the most important class of packet networks. In addition, in future there will be further transmission capacity intensive real-time services, such as, for example, the transmission of video data during a video-on-demand service.
An important class of real-time services is the automated provision of speech or video information. One example of this type of service is given by the recorded announcement services known from TDM networks, e.g. telephone number announcements (“the telephone number of the subscriber is . . . ”) or error messages (“the number you are trying to call is not available”). Thereby, automated information output can also contain subscriber specific information (e.g. telephone numbers). Dialogue functionality is an extension of the announcement functionality. There the user can control the service or the dialogue by using the keys in his terminal device or by means of speech input. Servers are used to achieve such kinds of services in packet networks. In the case of interactive services, the term IVR (interactive voice response) server is commonly used. A number of coding methods or codecs (coder-decoder), such as, for example, G.711A/u, G.723.1, G.726, G.728 and G.729A/B were standardized for the transmission of speech. Standards H.261 and H.263, for example, are used for the transmission of video information. For an information output, usually a codec or coding method that is supported by both ends of the network is selected for the information transmission in a so called codec negotiation.
For services with real-time transmission via data networks, it is essential that the service characteristics known from the TDM network be provided for corresponding or new services with comparable quality and efficiency. The optimization of the resource application plays an important part in this.